Chapter 37 - Guyton Flashcards
Define pulmonary ventilation.
inflow and outflow of air between the atmosphere and the lung alveoli
What is primarily responsible for expiration?
elastic recoil of the lungs, chest wall, and abdominal structures compresses the lungs
Muscles that help raise the ribcage during inspiration?
external intercostals, SCM, serratus anterior, scaleni
During heavy breathing, which muscles aid expiration?
abdominal muscles (internal intercostals also)
Pleural pressure
the pressure of the fluid in the thin space between the lung pleura and the chest wall pleura
What change occurs in the pleural pressure during inspiration?
expansion of the chest cage pulls outward on the lungs with greater force and creates more negative pressure (-5 to -8)
Alveolar pressure
the pressure of the air inside the lung alveoli
What change occurs in alveolar pressure during inspiration?
to drive air in, the pressure must fall (0 to -1 then +1 during expiration)
What is transpulmonary or recoil pressure?
the difference in pressure between the outer surface of the lungs and the alveoli, it is a measure of the elastic forces
What is lung compliance?
the extent to which the lungs will expand for each unit increase in transpulmonary pressure (200 mL)
The elastic forces of the lung tissue are determined
mainly by _____ and ______ fibers interwoven
among the lung parenchyma.
elastin, collagen
What is primarily responsible for collapse of the lungs, which force?
fluid-air surface tension forces in the alveoli represent about two thirds (rather than tissue elastic forces)
Secrete surfactant in the lungs.
type II alveolar epithelial cells
Primary role of surfactant?
greatly reduces the surface tension of water
Spirometry
record the volume movement of air into and out
of the lungs
Tidal volume (TV)
volume of air inspired or expired with each normal breath; it amounts to about 500 milliliters in the adult male
Inspiratory reserve volume (IRV)
extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force; it is usually equal to about
3000 milliliters
Expiratory reserve volume (ERV)
maximum extra volume of air that can be expired by forceful expiration after the end of a normal
tidal expiration; this normally amounts to about
1100 milliliters
Residual volume (RV)
volume of air remaining in the lungs after the most forceful expiration; this volume averages about
1200 milliliters
What is inspiratory capacity?
IC = TV + IRV; This is the amount of air (about 3500 milliliters) a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount.
What is the functional residual capacity?
FRC = ERV + RV; This is the amount of air that remains in the lungs at the end of normal expiration (about 2300 milliliters).
What is the vital capacity (VC)?
VC = TV + IRV + ERV; This is the maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent (about 4600 milliliters).
What is the total lung capacity?
The total lung capacity is the maximum volume to
which the lungs can be expanded with the greatest
possible effort (about 5800 milliliters); TLC = VC + RV
What is minute respiratory volume?
total amount of new air moved into the respiratory passages each minute; this is equal to the tidal volume times the respiratory rate per minute (average is 6 L/min = 500 mL tidal volume x 12 breaths per min)
